The present invention relates to a navigation system to be mounted on a vehicle or the like.
The vehicle-mounted navigation system has functions to set a destination, to search a route from the current place to the destination by the Dijkstra's algorithm or the like, and to guide the vehicle according to the searched route. The vehicle-mounted navigation system further has a function to be connected with an information providing device such as a server thereby to acquire useful information from that information providing device.
Japanese Patent Laid-Open Publication No. 2001-264088 (hereinafter, referred to as Patent Document 1) discloses a technique in which the information providing device transmits information concerning shops, parking areas or events to the navigation system through public networks, satellites or broadcasts.
In order to acquire the information, as described above, it is necessary to connect the information providing device and the vehicle-mounted navigation system. For this connection between the information providing device and the vehicle-mounted navigation system, enterprises and the like have provided, as services, base stations for short range communication (i.e., DSRC: Dedicated Short Range Communication) such as wireless LAN (Local Area Network), Bluetooth or ETC (Electronic Toll Collection). Usage charges for the base stations provided as services by the enterprises, are mostly free or low. From the viewpoint of communication costs, therefore, it is desired to communicate using the base stations for short range communication.
For communication with a base station within a short range, therefore, the vehicle mounted navigation system has to be so positioned as can communicate with that base station.
However, the vehicle-mounted navigation system is thought to move with the traveling vehicle so that it cannot always be located in an area in which communication with the short range base station is possible.